Helical hollow rotor pump



Mami: 8, 1949. J. B. WADE HELIGAL HoLLow no'ron Puur 3 Sheets-Sheet 1Filed Nov. 29, 1946 a l l l l I l Il llllfrl I l l A l I I l Il l I r ll l l l l Il March 8,1949. J. E, WADE 2,464,011

HELICAL HOLLOW ROTOR PUMP Filed Nov. 29, 1946 3 Sheets-Sheet 2 -lnvenor:falen Wade ,amd/4M N Homey Mmh s, 1949. J, B, WADE 2,464,011

HELICAL HOLLOW RO'I'OR PUMP Filed Nov. 29, 1946 s sheets-Sheet :s

1 d Eu/entor f@ fahrplan/ade Patented Mar. 8, 1949 HELICAL HOLLOW ROTORPUMP John B. wade, Arcadia, Calif., signor to Food Machinery andChemical Corporation, a corporation of Delaware Application November 29,1946. Serial No. 712,918

9 Claims. 1

'Ihis invention relates to improvements in Moineau type pumps.

In the Moineau type pump, shown in U. S. Letters Patent No. 2,028,407, ametal rotor provided with a wide, steeply-pitched helical thread isrotated within a central opening in a rubber stator. This opening has adouble internal helical Jthread so that a series of pockets or closedduid-tight spaces is formed between the rotor and stator, which moveaxially from the inlet end of the pump toward the outlet end thereof asthe rotor is rotated. Each of these pockets is generated While incommunication with 'the inlet end of the pump and thus sucks uidtherefrom and transports this fluid to and reverse direction to that inwhich the rotor is` rotated. The practice has been to make the rotorsolid and turn .this out on a lathe to produce the necessary helicalthread thereon.

Because of the revolution of the axis of mass of the rotor aforesaid, ithas been found expedient to connect the rotor to the line shaft with aflexible coupling. This has served -to transmit power from the lineshaft which rotates about a stationary axis to the rotor which rotatesabout a reversely revolving axis. At low speeds no difficulty resultsfrom this revolution ofthe rotor. It is the practice in well pumps,however, to turn the rotor 1500 R. P. M. or better. The vibrationproduced byvrotating a solid metal rotor at such speeds is excessive andtends to loosen up the connections oi the pump assembly and crystallizethe metal parts thereof.

It is accordingly an object of my invention to provide a Moineau typepump in' which this excessive vibration is eliminated.

The manufacture of rotors for Moneau pumps individually on a lathe is alaborious, expensive process. Machinery has been provided for makingthese automatically but this has been so expensive to yproduce as not togreatly reduce the cost of the rotors.

It is another object of my invention to provide a rotor for a Moineaupump and a method for producing the same whereby said rotors may be madeat a relatively low cost.

(Cl. 10S- 117) A considerable portion of any exible drive coupling usedfor driving the rotor o1 a Moineau pump revolves reversely with therotor and the lower portion of this coupling revolves over substantiallythe same path. I-t is` therefore important in reducing the vibrationcaused by this revolution of. the rotor to reduce to a minimum theweight of the connection between the coupling and the rotor. Y

Yet another object of my invention is to pr vide a combination couplingand rotor in which the connecti-on between the coupling and the rotor iseffected by means much lighter than originally employed for this purposeyet without sacrificing essential strength in the connection.

It has been recognized in the art to which this invention relates, andindeed is even pointed out in the aforementioned U. S. Letters Patent,that it is preferable for the rotor of a Moineau pump to have a densitywhich is practically equal to the density of the fluid in which itoperates in order to obtain a perfect equilibrium. Heretofore, however,no Way has been discovered of producing a practical Moineau type pumprotor which will have such a low density.

It is another object of fthis invention, therefore, to provide a rotorfor a Moineau type pump which will meet the exacting structuralrequirements of accuracy in helical contour and resistance to damageunder operating conditions but which, nevertheless, will havesubstantial-ly the same specific gravity as the liquid in which therotor operates.

Yet another object is to provide such a rotor which will be comparablein serviceability to the lightest rotors lpreviously available, whichwere turned from solid -bar stock and fthen provided with an axialcylindrical bore, and which have a specific gravity greatly in excess ofthat of water.

The manner of accomplishing ythe foregoing objects as well as furtherobjects and advantages will be made manifest in the followingdescription taken in connection with the accompanying drawings in which:

Fig. 1 is a diagrammatic longitudinal sectional view of a Moineau pump.incorporating a preferred embodiment of my invention.

Fig. 2 is an enlarged view of the novel rotor of my invention andillustrates the connection between this rotor and the flexible couplingassociate dtherewith.

Fig. 3 is a vertical elevational view on the same scale as Fig, 2 andpartly broken away to illustrate the means for connecting the upper endof the flexible coupling with the line shaft.

Fig. 4A is a View similar to Fig. 4 illustrating' another modified meansfor connecting the rotor and coupling.

Fig. 5 is a plan view of a novel mold of my invention opened as whencommencing operations.

Fig. 6 is a perspective view of said mold when so opened.

Fig. 'I is a perspective view of one of the clamping rings employed inconnection with said mold.

Fig. 8 is a rotor lapping machine employed in performing the method ofmy invention.

Fig. 9 is a fragmentary detail view taken on the line 9-9 of Fig. 8.

Fig. 10 is a front elevational view of the aforesaid mold with thelatter opened and illustrating the insertion into said mold of a sectionof tub'- ing when starting to perform the method `of my invention.

Fig. 11 is a vertical sectional view of said mold Aillustrating themanner of applying the clamp- Fig. 13 is an enlarged fragmentarysectional' view of the base of the mold of my invention.

Referring specifically to the drawings, my in- 'vention is shown thereinas embodied in a Moineau pump I0 which is suspended from the lower endof a string of pump tubing II in a well I2 having an outer casing I3.The tubing II is made up of sections between which are mounted bearingspiders I4 having bearings I5 in which is journaled a rotary line shaftI6.

Ihe pump Ill includes a housing I9 which is threadedly connected withthe lower end of the pump tubing II and is provided at its lower endwith a grating to strain water entering the pump I0. Provided within thehousing I9 is a rubber Moineau stator 2l having an opening 22 throughwhich a Moineau rotor 23 extends. The stator 2| and the rotor 23 havethe characteristic congurations respectively of the stator and the rotorof the Moineau type pump, in which the opening 22 has a double helicalfemale thread and the rotor 23 has a single male thread of the samepitch length.

The rotor 23 is driven by the shaft I6 through aA flexible coupling 25which connects the lower end of this shaft with the upper end of therotor.

The outer conformation of the rotor 23 of my invention has a single malethread 26 of exactly that form and pitch as will cause it to produce apumping action when rotated in the stator 2 I. This conformation must bemathematically exact within a very small tolerance.

To cause the rotor 23 to be of exceptionally light weight as comparedwith the Moineau pump rotor formerly in common use I form this ofrelatively thin sheet material which is preferably a ductile metal.While various methods may be used in producingthe rotor 23, I have foundit preferable to forml this by expanding aA ductile annealed steel tubeinto conformity with a mold, the cavity of which has a shapecorresponding to the desired shape ofthe rotor 23, although slightlylarger in radial dimensions so that when pressure is relaxed from theinterior of the tube the latter will contract to approximately exactly 4the desired shape of the rotor 23. This tubular shell 30 comprises themain body of the rotor 23 and is produced in the following manner:

The apparatus for manufacturing the shell 30 includes a mold and alapping machine 36, these being illustrated in Figs. 6 and 8respectively. The mold 35 is for forming the shell 30 into approximatelyits desired shape and the lapping machine is for the purpose ofperfecting the outer contour of the shell 30.

of rails 42 so that a central boss 43 of the base extends downwardlybetween the rails 42. TheseA rails are connected by shafts 44 on whichare pivoted eye bolts 45.

The base has a shallow upward boss 43 which has the -same outsidediameter as a mold body 49 mounted thereon. The base 40 has a. hole 50extending upwardly therein, this hole having a counter-bore 5I with anenlargement 52 at its upper end adapted to form part of'a mold cavity 53provided in the mold body 49.

Extending upwardly through the hole 50 is a hydraulic injection pipe 54having a cap 55 screwed onto its upper end. The cap 55 has a squared end56 and is centrally apertured to a1- low hydraulic fluid to be deliveredfrom the pipe 54I into the interior of the mold. Surrounding the pipe 54within the counter-bore 5I beneath the cap 51 is a washer 5B and arubber packer 59. It might be noted here that the diameter of thecounter-bore 5I is such as to snuggly receive the lower end of a tube 65employed in the process and the washer 58 and the packer 59 snuggly fuitthe interior of Ithis tube when so received. d 1

The mold body 49 is formed of a low temperature casting metal and itoriginally kis cast as a unit about a turned master rotor having exactlythe configuration which it is desired to produce in the rotor 23. Themaster rotor is then screwed out of the casting and the latter is sawedinto three segments 66, 61 and 68. These lsegments are then providedwith radial plates 69, 10 and 1I, the inner edges of which are ground toaccurately complement the surfaces of the mold cavity 53 formed in thesegments 66, 61 and 6B of the mold body 49 when the latter wasoriginally molded.

The plates 69, 10 and 1l are slightly thicker than the kerf formed bythe saw when dividing the mold body into these segments so that the moldcavity 53 is slightly larger, as measured from the axis thereof, thanthe rotor shell 30 which it is desired to produce therein. This, aspreviously explained, is due to the fact that in forming the shell 30 inthe mold 35, tube 65 is expanded hydraulically and allowance must bemade in the sizel of the mold cavity 53 for the inevitable contractionof the tube 65 away from `the surfaces of the mold cavity 53 when thehydraulic pressure inside the tube is relaxed.

The segment 66 is fixed on the boss 48 and the segments 61 and768 areconnected by hinges 12 to the segment 66`.` Annular ring seats 18, 19and are provided with the same inside diameter as the external diameterof the mold body 49 when the segments 66,61 and 68 thereof are swungtogether. These ring seats are divided as clearly shown in Figs. 5 and 6and the respective sections thereof secured to the mold segments 66, 61and 6B so that when these segments are swung together the ring seats 18.1.9 and 80 will surs round the mold body 49 and provide tapered surfacesadapted to be engaged by the tapered inside Vsurfaces 8| of a series ofclamping rings 82,

To complete the assembly of the mold 35 a mold head 90 is applied to thetop of the mold body 49, this mold head having a flange 9| which snuglyreceives the upper end of the mold body. The mold head 90 has anupwardly extending boss 92 which carries opposite pairs of clamp arms 93between which the eye bolts 45 extend to clamp down on these arms andthus hold the head 90, the .mold-body 49 and the base 40 from beingseparated vertically during the molding operation.

The mold head 90 has a hole` 94 in which is formed a counter-bore 95,the latter having an enlargement 96 at its\lower end Which complementsand unites with the upper end of the mold cavity 53.

Extending through the hole 94and the head 90 is an air relief pipe 91having a lower head 98 which traps a washer 99 and a packer 00 in thecounter-bore 95. ',Ihe counter-bore is of the same diameter as thecounter-bore and the washer 99 and packer |00 are of the same diameteras the washer 58 and packer 59. Thus when the mold 35 is assembledwiththe annealed steel tube 65 disposed therein, as shown in Fig. 11, andthe head 90 applied as shown in Fig. 12, the upper end of the tube 65extends snugly into the counter-bore 95 and about the washer 99 andpacker |00. The pipe 91 is provided with a nut |0| and comprising a pairof -rigidly spaced channels ||0 on which are mounted a motor a lathehead ated to cause the reversal of the motor thereby reversing the'direction of the movement of the nut |30 0n the shell 30. Thiscontinues until the arm |3| engages arm |26 which actuates the switch|2| to again reverse the motor to cause the nut |30 to return in theopposite direction. Thus the nut |30 is caused to ride back and forth onthe shell 30 so that by placing `a grinding compound between the nutand. the

shell and keeping the nut snugly tightened up on the shell, the latterwillbe lapped into conformity with the nut |30.

Operation While the tube 65, of which the rotor 23 is formed, may bemade of any of a variety of materials, it has -been found preferable touse a metal which is resistant 'to corrosion by the liquid to be handledin the pump in which the rotor is to be employed and then coating therotor with a layer of chromium applied electrolytically, Among themetals suitable for this use, Chromium-nickel 18-18 stainless steel hasbeen found preferable. seamless is preferred, although it is practicalto use a welded tube from vwhich the ash has been removed. l

The tube 65 is cut to the proper length so that its lower and upper endsextend into the counterbores 5| and 95 and against the bottom shouldersrespectively thereof, when the mold 35 is stock ||2 and a lathe tailstock ||3, the motor being connected by any suitable means such as abelt ||4 -to the head stock H2. The head stock hasel chuck ||5 and thetail stock a collar H8, the latter being adapted to center one end of ashell 30 when the opposite end is gripped in the chuck I 5.

The motor has a hand switch |20 and an automatic reversing switch |2|,the latter being actuated by the longitudinal shifting of a rod |22which slides in blocks |23 and |24 provided on one of the channels ||0.The rod |22 has two arms |25 and |26 which extend horizontally over thespace between the two channel arms 0. Adapted to be screwed onto a shelland remain thereon while the latter is being operated on by the machine36 is a split lapping nut |30 having an arm |3| extending downwardlytherefrom with a roller |32 on its lower end which is adapted to rideagainst one or the other of the channels ||0. The nut |30 has a clampingbolt |35 by which the nut can be tightened or relaxed as desired. Thenut |30 has internal threads formed by casting the same around the samemaster rotor which the mold body 49 was formed from so that the nut |30is adapted to threadedly receive a shell 30 asshown in Fig. 8.

When the switch |20 is closedthe motor starts to rotate the shell 30 inthe machine in a direction to cause the nut |30 to travel either to theright or to the left. Switch |2I is so connected that, when, due to thistravel, the arm |3| engages the arm |25, the switch |3| isactucompletely assembled as shown in Fig. 12.

Afterthe tube 65 has been inserted as shown in Fig. 11, and before themold head is applied, a Wrench is inserted through the tube 65 and thesquared end 56 of the cap 55 turned to screw this onto the pipe 54 andexpand the packer 59 within the lower end of the tube 65. After the head90 has been applied, this is clamped down as shown in Fig. 12 byswinging the eye bolts 45 into vertical position and screwing the nutsthereof downwardly against the clamp arms 93. The nut |0| is thenrotated to lift the pipe head 98 and thus expand the packer |00 in the fupper end of the tube 65.

Before the tube 65 is inserted into the mold and the latter assembledthereabout, as just described, the tube is subjected to a thoroughannealing by heating this to a cherry redand then quenching it in water.

With the tube thus annealed and assembled with the mold and with the'air bleedervalve |0| open, the pipe 56 is connected to a high pressurehydraulic pump and the latter operated to inject liquid through the pipe56 and cap 5l into the interior of the tube 65. The valve |0| is leftopen until the liquid rises, fills 'the tube 65, and starts to dischargefrom the valve, whereupon the latter is closed.

As the hydraulic pressure in the tube increases beyond the capacity ofthe tube 65 to resist distortion, the latter is expandedoutwardly topartial conformity with the mold cavity 53.

Owing to the tendency of a tube 65 of this particular material to burstwhen attempting to expand it into complete conformity with the moldcavity 53 in one stage, I have found it preferable to employ severalstages in expanding the tube before finally reaching the desired shape,and removing the tube from the mold and annealing the same betweensuccessive stages in the ex. pansion thereof.

When returning tube 65 to the mold after it has been thus partiallyexpanded and removed for annealing, it must be returned in exactly theTubing of this material which is rotor known as No. Moineaurotor whichhas l0 a diameter of 2.008" after plating, a tube 65 which is of 16gauge material with a 11A" outside diameter is quite suitable. g

Escape of liquid from Opposite ends of the tube 65 during one of theexpanding operations is pre- 15 vented by the expansion of the packers59 and |00 in the lower and upper ends of the tube 65 where these aredisposed in the counter-bores 5|' and 95 respectively.- The higher thepressure'of the liquid in the tube 65 the tighter the seal 20 formed bythe packers 59 andv |00 to prevent-the escape of liquid from the tube.

To remove the tube 65 from the moldv 35 after it has been partially orfully expanded to form a rotor shell 30, the process of assembling the vl sockets |12 and |16.

tube 65 with the mold and above described is merely reversed. JNhen theshell has been formed as completely as it is possible to do this in themold 35,

there still remainimperfections in the outer-sur- 30 face of the shell30 whihgnust be eliminated andr this surface then providedwlth vaprotective coating of chromium.

The perfecting of the contour of ththread 26I on the rotor shell 30 isaccomplished in tire-1151.152:`A 35 ping machine 3B. Beingformed-directly from ai; r`

master rotor of the exact shape which i-s'desired to be given to therotor shell 30, the lapping nut |30, when supplied with a grindingcompound and put to work on the shell 30 in the machine 4u 36, asalready described, will smooth the outer surface of the shell 30 andbring this into very close approximation of the conformation of themaster rotor.

The lapping operation is also preferably car- 45 ried-on in three stageswith coarse, medium and fine grinding compounds, the iinal stages beinga polishing operation.

The lapping and polishing of the rotor shell 30 is carried out with aview t0 finishing with 50 the rotor being at least .004" less indiameter than the desired final size of the rotor shell. A coating ofchromium is then applied electrolytically to the outer surface of therotor shell which may be anywhere from .002" to .004" in thicknessdepending upon what it is necessary to add to the diameter of the shell30 to give it the out side diameter it should have in order to cause itto function properly in the stator 2|.

This chromium is applied to the shell 30 in the 60 same manner as it isnow customary to apply chromium to shafts where these rotate in waterlubricated rubber bearings.

Theupper and lower tubular ends |45 and |46 of the shelll 30 remaincylindrical without chang- 65 ing diameter throughout the expansion ofthe tube 65. 'I'he bottom tubular end |46 may be shortened as shown inFig.v 2 and closedv by a Aplug |48 welded therein'. The upper tubularend |45 .is preferably utilized to form a connection 70 Three modes ofperforming this connection are illustrated herein, one of these beingshown in Fig. 2, another in Fig. 4, and still an-` other in Fig. 4A. p

The coupling 25 is` of the general type disclosed Vin U. s. LettersPatent of James M. Hau, No. 2,346,426, issued April 11, 1944, onFlexible rotary drive coupling. AThis 'type of coupling comprises asteel cablev |1|, the upper end of which extends into and is securelyheld in a cable socket |12 of a coupling head |13 having a screwreceptacle |14 which screws onto the threaded lower end |15 of the shaftI6.

In Fig. 2 the cable |1| .is shown as connected to the rotor 23.by theswedging of a light steel socket |16 thereabout, and then welding thissocket, which constitutes a lower coupling terminal member, into theupper tubular end |45 of the shell 30., The mouths |11 and |8I ,of thesockets |12 and |16 are ared and the entire cable |1| and substantialportions of the sockets |12 and |16 and the rotor neck |45 are coveredVwith a rubber sheath |85'Which'is vulcanized in place so as to extendinto the flared socket mouths |11 and |8| and thus form a cushionpreventing the cable |1| being sharply bent adjacent the It isfrequently desirable to disconnect a rotor 23 from a flexible coupling25 where one of these needs to be replaced whilethe other is still good.

This is` made readily possible by the construction.

shown in Fig. 4. In this construction the upper tubular end |45 of theshell 30 is cut off rather short and receives a nipple formed on thelower end of a short internally threaded socket |9| having the sameoutside diameter as,the tubular shell end |45. The two are then weldedtogether so as to permanently unite the socket |9| with the rotor shell30. When this construction is used the lower end of the flexiblecoupling 25 has a socket |94 which 'receives and is swedged about thelower end of the cable |1| vand in turn is provided with threaded malemember |95,l which screws into the threaded socket |9|.

As shown in Fig. 4 the flexible coupling 25 and member |94 have the sameoutside diameter as the socket |9| and upper tubular end |45 of theshell 30. Thus there is a of interference with the flow of water fromthe pump I0 upwardly through the pump tubing The rotor 23 of myinvention weighs approximately one pound, whereas the solid rotor made'of stainless steel, which has preceded it in common use, weighs sevenpounds. Moreover, since the solid rotor must be'turned from a solidpiece of stainless steel which weighs ten pounds, it is readily seenthat the method of my inventionl oiers an opportunity to produce aMoineau pump rotor with a saving of about 90% in the amount of thecritical materials required. It is further evident that by my methodMoineau pump rotors may be produced at a great saving in expense overthe cost of producing rotors by turning these from a solid piece ofstainless steel.

A still moresignicant advantage of the rotor 23, however, is itsextremely low weight and the marked decrease in the amount of vibrationproduced by my rotor over the vibration produced with solid rotors. Theextreme low weight of the rotor 23 results, of course, from its beingfromed of a shell of substantially uniform thickness, and its beingclosed at its lower end by the plug |48 and at its upper end by itsconnection with the coupling 25 so that the rotor remains hollow orempty, although during its operation it is continuously submerged in aliquid.

closing of the upper end of the rotor 23 so as toeiectively prevent theadmission of liquid to the hollow interior thereof, (in the form of therotor shown in Fig. 2) is accomplished by completely enclosing thecoupling cable, exposed portions of the socket |16, and theupper tubularend |45 of the shell 30 within the rubber sheath |85 and vulcanizingthis sheath to these metal parts as shown in Fig. 2.

The welding of the nipple |90 into the upper tubular end .|45 of thesneu so of the rotor' 23 also makes a liquid tight conection between theupper end ofthe rotor 23 and the threaded socket I9 I. When the latteris screwed into the threaded male member |95, a suitable sealingcompound.,

such as paint, is used onthe threads to make the connection between thecoupling socket |94 and the threaded socket l9| on the rotor, therebyforming a liquid tight closure for the upperend n of the rotor. .l q

The closing of the lower end of the rotor 23 by Welding the plug |48therein hermetically seals the lower end of the rotor against theadmission of liquid and it has been found preferable to alsohermetically seal the upper end of the rotor in a similar manner asshown in Fig. 4A. In this,

view the rotor 23 is showniitted with a threaded socket |96 having aplug |9Tflwhich ts into and is welded to the upper tubular en dilfipfthe shell 3U of the rotor 23 so as'to hermeticallysal the upper end ofthe rotor against the'admissionof liquid into the hollow interiorthereof.

This application is a continuation in part of my co-pending U.v S.Letters Patent application, Serial No. 553,626, iled September 11, 1944,for Moineau pump coupling-rotor and method of making same," nowabandoned.

The rotor 23 of my invention of the type shown in Fig. 4A and which ismade in accordance with the foregoing data is substantially of the sainespecific gravity as water, Iwhich is the liquid that Moineau pumps areordinarily employed for handling.

The claims are:

1. A gear mechanism adapted for use as a pump and comprising: a statorhaving a femalethreaded chamber, the latter having an inlet and anoutlet communicating therewith at axially spaced points; and athin-walled, male-threaded rotor comprising a tube which, throughoutsubstantially its entire llength, is 'hollow and has walls ofsubstantially uniform thickness, said tube being plugged at oppositeends so as to seal the hollow interior thereof against the admission ofliquid thereto and being revolubly disposed in said chamber and alwaysin contact therewith in any cross section, the number of female threadsof the stator exceeding by one unit the corresponding number'of malethreads on the rotor, a closed fluid-tight axial space being comprisedbetween said stator and rotor wherein the fluid is contained, rotationof said rotor generating a continuous series of said spaces, each suchspace being in communication with said .inlet while being generated,said rotation causing each such space to then travel in an axialdirection until coming into communication with said outlet and thencausing said space to be contracted until dissipated, iluid thus beingtransferred from said inlet to said outlet, said rotor, because of itslightness; producing a radically less amount of vibration than isproduced by a like rotor of solid construction when so rotated in saidstator.

2. A gear mechanism adapted for use as -a pump and comprising: a statorhaving a. femalei threaded chamber, the latter having an inlet and anoutlet .communicating 'therewith at axially spaced points;A athin-walled male-threaded rotor comprising a tube which, throughoutsub-v stantially its entire length, is hollow and has walls ofsubstantially uniform thickness, said tube being plugged at oppositeends so as to seal the hollow interior thereof against the admission ofliquid thereto, said rotor being revolubly disposed in said chamber andalways in contact therewith in any cross section, the number of femalethreads of the stator exceeding by onev unit the corresponding number ofmale threads on the rotor, a closed iiuid-tight axial space beingcomprised between said stator and rotor wherein the fluid is contained,rotation of said rotor generating a continuous vseries of saidspaces,each such space being in communication with said inlet while beinggenerated, said rotation causing each such space to then travel in anaxial direction until coming into communication with said outlet andthen causing said lspace to be contracted until dissipated, iluid thusbeing transferredfrom said inlet to said outlet, the plugging means atone end of said rotor constituting a detachable connection between therotor and a driving means therefore, said rotor, because of itslightness, producing a radically less amount of vibration than isproduced by a like rotor of solid. construction when so rotated ginsaidstator. l

,3. A hollow male threaded pump rotor of relativelylight weight adaptedto rotate at high speeds in a female threaded stator whereby said rotoris caused to revolve about an axis eccentric to the center of mass ofsaid rotor and in the opposite direction to said rotation, said r0- torcomprising a tubular shell which, throughout substantially its entirelength, is hollow and has walls of substantially uniform thickness, saidshell being sealed at its opposite ends .against the admission of liquidthereto, the means for sealing one end of said rotor having meansthereon for connecting said rotor with a driving means therefor, saidrotor, because of its lightness, producing a radically less amount ofvibration than is produced by a like rotor of solid construction when sorotated in said stator.

4. A combination as in claim 3 in which one end of said rotor has anaxially disposed integral tubular neck, the sealing means 'connectingsaid rotor with a driving means therefor being housed within and bondedto said neck.

5. A combination as in claim 4 in which said sealing means housed withinand bonded to said tubular neck comprises a cup which provides adetachable connection between said hollow rotor and said driving means.

6. A hollow pump rotor as dened in claim 3 in which said connectingmeans comprises a exible cable having a head permanently unitedtherewith, said head being also permanently bonded with one end of saidrotor whereby rotation of said cable is transmitted to said rotor andsaid'head forms the sealing means for said end of said rotor.

7. A hollow pump rotor as defined in claim 3 in which said connectingmeans comprises a ilexible cable having a head permanently unitedtherewith and with one end of said rotor to form the sealing meanstherefor and to connect said A l l cable to said rotor,v said end ofsaid rotor and said head and said cable being covered by a sheath ofsoft rubber molded thereon and bond- Aed thereto.l

8. Ahollow pump rotor as deiined in claim 3 in which the means forsealing one end of said rotor and connecting the rotor with a drivingcup which fits within said rotor end and is bonded thereto; amale-threaded drive coupling head adapted to screw into said cup; and aVflexible drive coupling element united with said head.

9. A gear mechanism adapted for use as a pump and comprising: a statorhaving a femalethreaded chamber, the latter having an inlet and an.-outlet communicating therewith at axiallyspaced points; a hollow,thin-walled ma1e. threaded, tubular rotor revolubly disposed in saidchamber and always in contact therewith in any cross section, the numberof female threads of the stator exceeding by one unit, the correspondingnumber of male threads on the rotor; a plug closing one end of saidrotor; bearing means disposed concentrically with said stator; a shaftjournalling in said bearing means and spaced axially from said rotor; aiiexible coupling comprising two heads connected by a fiexible cable,one of said heads being xed upon means therefor includes an internallythreaded said shaft and the other of said heads extending into the otherend of said hollow rotor and being bonded thereto to seal the sameagainst the admission of liquid thereto and to transmit torque from saidcoupling to said rotor; and a rubber coupling sheath which covers andseals the connection between said hollow rotor and said coupling.

JOHN B. WADE.4 REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 21,374 Moineau Feb. 27, 1940736,039 Wainwright Aug. 11, 1903 1,702,047 Fulton Feb. 12, 19292,028,407 Moineau Jan. 21, 1936 2,212,417 George Aug. 20, 1940 2,267,459Halt Dec. 23, 1941 2,346,426 Hait Apr. 11,-1944 FOREIGN PATENTS NumberCountry Date 780,791 France Feb. 11, 1935 Certiicateof Correction PatentNo. 2,464,011. March 8, 1949.

JOHN B. IWADE It is hereby certified that errors appear in the printedspecification of the above numbered patent requiring correction asfollows:

Column 2, line 14, for the Word originally read ordinarily; lines 50 and51, for associate dtherewth read associated therewith; column 6, line23, for IS-18 read 18-8; column 8, line 70, for fromed read formed;column 9, line 32, for en c1145 read end 145;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Oce.

Signed and sealed this 9th day of August, A. D. 1949.

THOMAS F. MURPHY,

Assistant Gommasoner of Patents.

